In order to stabilize and increase hydrocarbon process gas (wet gas) delivery from a production well, whether subsea or topside, a compressor is usually installed downstream of a coarse liquid separation, The compressor requires a drive motor with a high power rating, usually in a current range of 500-2000 A and a voltage range of 6.6-12 kVAC.
It is important to cool the motor, an in doing so the process gas obtained from the production well is used as a cooling medium. In turn, this implies that the power cables to the motor as well as the penetrator assembly will be exposed to a wet gas environment at high temperatures, typically in the range of 70° C.-200° C. and at a high pressure in the range of 100-400 bar.
The gas which is used for cooling the motor is both wet, as it may contain water, and polluted, as it normally will contain electrically conductive particles and a large variety of other impurities which may lead to electrical flash-over, creep currents and voltage breakdown. In a worst scenario, such operating conditions may lead to ignition of the production gas and explosion, with catastrophic consequences.
Further, during a wet gas production, a rapid decompression may occur, and as a result devices such as O-rings and electrical insulation which have been exposed to high pressure, may simply explode, giving rise to the risk of fatal breakdown of the compressor subsea installation.
In view of on one hand to require optimum withdrawal of gas from a production well and therefore the need to increase the pressure therein to expel the gas from the reservoir, and on the other hand the tough and hazardous environment in which a subsea compressor unit has to work, with related implications if an operation failure is about to happen and is not detected in time to take counter-measures to prevent it happen, has been a headache to the profession and a challenge which has existed for years without a satisfactory solution to overcome the well known operational problems.
It has therefore been a the prime object of the present invention to provide a technical solution which will remedy the deficiencies of the prior art solutions or at least reduce the operational hazards to an absolute minimum, thereby gaining operational stability, longer life of the compressor and its motor, and in turn improved cost-benefit rating.